We'd still be able to make relays, and that's enough to do computing. If not that, then mechanical computer systems could be constructed to process data.

There's enough information on machine tools and the working of iron to make all the tooling and machinery required to start an assembly line somewhere.

After all, there was an assembly workshop turning out the Antikythera mechanism, there was a user guide on it. Obviously it wasn't the only one produced at the time.